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The steepest motorway

Design standards for motorways (and their intersections) require that gradients should be no steeper than 4% (1 in 25) except that in exceptional circumstances, gradients of 5% may be used over short lengths. Between the Shore Road and Sandyknowes section of the M2 in Northern Ireland, the gradient reputedly reaches 1 in 19½ (5.13%) in places. Shortly before the contract was let it was decided that a crawler lane should be added on this outward carriageway.

Steep gradients are often found on complex interchanges, but where the M90 terminates at the Craigend interchange with the southern by-pass to Perth, the topography dictates gradients said to be well above the recommended maxima. The actual gradients achieved are not yet known.